Gemfibrozil, or 5-(2,5-dimethylphenoxy)-2,2-dimethylpentanoic acid, is a widely used antihyperlipoproteinemic agent. While apparently absorbed throughout the gastrointestinal tract, maximum absorption appears to occur in the upper gastrointestinal tract and this is true notwithstanding the poor solubility of the drug at acidic pH.
Prior attempts at developing sustained release formulations, as for example reservoir systems, have not met with a great deal of success, producing either inadequate bioavailability or unacceptable release profiles. Paradoxically, it appears the achievement of a sustained release formulation requires disintegration or erosion in the stomach and upper gastrointestinal tract.
British Application No. 2,179,254 discloses compositions of analgesic propionic acid derivatives (such as ibuprofen) coated with a methacrylic-acrylic copolymer, then with a methacrylic ester copolymer, and finally with a mixture of polysorbate 80 and hydroxypropyl methylcellulose.
EPO-A No. 8600802 discloses sustained release compositions of polyethylene glycol and an amphiphilic compound.
French Application No. 2,554,717 discloses sustained release compositions which employs as the matrix a vinylpyrrolidone-vinyl acetate copolymer and an acrylic polymer cross-linked with polyallyl sucrose. (See also Belgian application No. 901007.)
U.S. Pat. No. 4,132,753 discloses controlled release granules in which the powdered medicament is heated so as to sink into a finely divided wax material.
U.S. Pat. No. 4,195,084 discloses a liquid suspension of finely ground tall oil sitosterols for use in reducing hypercholesteraemia.
U.S. Pat. No. 4,263,272 discloses three component formulations of bile acids which release gradually or in two stages.
U.S. Pat. No. 4,291,016 discloses pharmaceutical compositions having a matrix core coated with hydroxypropyl methyl cellulose.
U.S. Pat. No. 4,533,562 discloses tablets coated with a film-forming polymer such as hydroxypropyl methylcellulose and a liquid plasticizer such as polyethylene glycol.
U.S. Pat. No. 4,661,162 discloses an enteric soluble composition containing a mixture of an enteric-soluble polymer such as (m)ethyl acrylate/methacrylate copolymers and a polyanionic polymer such as alginic acid and its salts.